Heart Rate Exertion
Heart Rate Exertion measures the total exertion for a session based on weighted heart rate values. Each heart rate value is assigned an exertion value based on a heart rate exertion weighting function (see image).
The weighting function is based on the heart rate relative to max heart rate and uses weightings accepted in the industry. The exertion values are multiplied by the time between successive heart rate values in seconds (usually 0.1 seconds) and then totaled.
The below formula is used for the calculation:
HR Exertion = C ∑ Wi dti
Where
• i = 1 to n, the number of time points C = scaling constant = 0.0167
• Wi = Heart Rate Exertion Weighting for Time point ibased on HR/Max HR (see graph)
• dti = Ti – Ti-1, time interval in seconds between successive HR values (usually 0.1)
• n = number of HR value
Example
Suppose you are monitoring a person's heart rate during a 5-minute exercise session with a heart rate monitor that records data every 0.1 seconds (dti = 0.1 seconds). You have 3000 data points (n = 3000), and you want to calculate the HR Exertion using the formula.
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You start with the first data point, let's say HR = 120 beats per minute (bpm), and Max HR = 180 bpm. You calculate Wi for this point based on the ratio: Wi = 120 / 180 = 0.6667.
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You move to the next time point, and let's say the HR is 123 bpm. You calculate the time interval (dti) as 0.1 seconds (since data is recorded every 0.1 seconds). You calculate Wi based on HR = 123 and Max HR = 180, which = 0.6833.
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You continue this process for all 3000 data points, calculating Wi and dti for each point.
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Finally, you sum up all the individual products of Wi and dti for all time points (from i = 1 to 3000), and multiply the sum by the scaling constant C (0.0167).
HR Exertion = 0.0167 * (Σ (Wi * dti) for i = 1 to 3000)
This final value, HR Exertion, gives you a quantified measure of the person's exertion level during the 5-minute exercise session based on their heart rate data and how it relates to their maximum heart rate, with a more granular time interval of 0.1 seconds between data points. The result will be a numerical value that indicates the overall exertion level during the exercise, with higher values indicating greater exertion.